Functional characterization of two proteins involved in generating the 3'ends of mRNA in bacteria and yeast.

摘要: E. coli termination factor rho requires an additional transcription factor, nusG, at many sites in vivo. In vitro, we have shown that nusG protein causes a promoter-proximal shift in rho-dependent termination endpoints. Assays of rho activity in RNA binding, ATPase and helicase function were unaffected by nusG, but with stalled elongation complexes we have demonstrated that nusG mediated the release of a shorter-than-normal subset of RNAs independent of the rate of elongation. We have inferred that nusG activity does not depend upon the kinetic coupling between rho and RNA polymerase.A model to account for these effects is supported by several observations. First, the off-rate of rho from ternary complexes stalled within $ trp\t\sp\prime $ was slower when nusG was present. Second, if rho termination was blocked by DNA oligonucleotides complementary to particular segments of the normal rho binding site …